Development of two-color digital holographic PTV for dispersed two-phase flow

Abstract

Bubbly flows have been widely used in various industrial fields such as the drag reduction of ships and the purification of water. It is expected to investigate the three-dimensional mechanism of the two-phaes flows which involve bubbles with various sizes. Digital holographic particle tracking velocimetry (DHPTV) is an effectual tool for making the flow structure clear, because DHPTV enables to measure instantaneous three-dimensional time series velocity fields of bubbles without complicated optical systems. In a holographic image, microbubbles are recorded as fringe patterns and a millibubble is recorded as a shadow image. The objective of the present study is to establish the measuring method for the velocity of bubbles with micro- and milli-meter sizes by using two laser beams. Finally, the method was realized by combining stereo holographic technique and stereo shadow imaging technique. A millibubble was measured by stereo shadow imaging technique and microbubbles were measured by stereo holographic technique.